1. Field of the Invention
The present invention relates to an electrostatic capacitance sensor for detecting approach of a human body or the like, and a flap type handle having an electrostatic capacitance sensor containing the main body of the sensor.
2. Description of Related Art
An electrostatic capacitance sensor is installed in a door handle of a vehicle as disclosed in JP-A-2003-221948 (Patent Document 3), for example, and it is used as a sensor for detecting approach of a human body to the door handle by generating a trigger of a signal transmission to a portable device in a keyless entry system.
A conventional general electrostatic capacitance sensor is designed to be electromagnetically provided in the form of a single body as a sensor body, and it detects variation of electrostatic capacitance (floated capacitance) formed by a detection electrode of the sensor body and a detection target facing the detection electrode to detect the presence or absence of the detection target.
JP-A-2002-147117 (Patent Document 1) discloses an automatic door using an electrostatic capacitance sensor using an electrically conductive vapor-deposited film, electrically conductive print or the like as a detection electrode in order to enlarge the detection range of the sensor. Furthermore, JP-A-2004-150869 (Patent Document 2) discloses a proximity sensor for enhancing detection capability (detection range, etc.) by combining the detection portion of an electrostatic capacitance sensor with dielectric material (for example, cloth). However, the Patent Document 2 has no detailed description on how the dielectric material is combined.
In the case of the conventional general electrostatic capacitance sensor described above, the sensitivity adjustment (containing adjustment of sensitivity balance, setting of the detection range) is carried out by adjusting the electrode size or adjusting the gain of the detection circuit. However, in this construction, it is required to change the dimension and shape of the detection electrode and the gain of the detection circuit (set different optimal values) in accordance with applied conditions such as the dimension and shape of a fixing portion of the sensor (for example, the dimension and shape of the door handle), required sensitivity, etc., and this is problematic. When it is required to change the dimension and shape of the detection electrode in accordance with the applied condition, it is required to produce plural kinds of sensor main bodies in accordance with the applied condition, and this is disadvantageous in production cost, part managing cost. Furthermore, when the gain of the detection circuit is required to be changed in accordance with the applied condition, plural kinds of detection circuits in which different gains are set in advance are required to be produced in accordance with the applied condition, or it is required to carry out a work of adjusting the gain of the detection circuit at the fabrication time case by case. Therefore, this is disadvantageous in production cost, part managing cost.
In the case of the sensor disclosed in the Patent Document 2, by varying the size of the dielectric material (for example, cloth) combined with the detecting portion of the electrostatic capacitance sensor, the detection capability (the detection range, etc.) can be changed without changing the dimension and shape of the detection electrode of the sensor body. However, in this case, large difference in sensitivity occurs between the contact portion between the dielectric material and the sensor body (the overlap portion between the detection electrode of the sensor body and the dielectric material) and the portion of only the dielectric material, and it is difficult to equalize the sensitivity distribution as a whole (that is, the difference in detection sensitivity with respect to the position is reduced, the balance is adjusted to desired one), for example.
For example in the case where the sensor body is installed in a door handle or the like as disclosed in the Patent Document 3, if a gap (space) occurs between the inner surface of the member constituting the door handle or the like and the dielectric material or between the dielectric material and the detection face of the sensor body, foreign material invades into this gap and the detection sensitivity is varied.
Furthermore, there is no prior art in which an electrostatic capacitance sensor is installed in a flap type handle having a complicated construction, and it is a problem how to dispose the sensor body in the flap type handle and how to secure the performance such as the detection range, etc.